1. Field of the Invention
This invention relates to a method of examining insulation displacement connection, for example, in the production of a wire harness, and also relates to an apparatus for performing this method.
2. Description of the Related Art
As shown in FIGS. 7 and 8, a wire harness, for example, comprises parallel wires 50 each having a conductor 51 coated with an insulating resin 52, connectors 30 connected to the wires 50 at suitable regions in a lengthwise direction and a widthwise direction, and covers 31 attached to the respective connectors 30 if necessary. In view of the efficiency of the operation, insulation displacement fitting connector (hereinafter referred to as xe2x80x9cinsulation displacement connectionxe2x80x9d) as shown in FIG. 8 has now been increasingly used for connecting the wires 50 to the connector 30.
As shown in FIG. 8, in this insulation displacement connection, a vertically-movable, insulation displacement connecting blade holder (not shown), having insulation displacement connecting blades 10 corresponding respectively to the wires 50, is moved downward, and a distal end surface of each of the insulation displacement connecting blades 10 press-fits the associated wire 50 into slots 41 a of an associated insulation displacement connecting terminal 40 of the connector 30, so that the wire is held in the terminal 40 by pinching, produced in the terminal 40 at this time, and hence is connected to the terminal. During this press-fitting operation, the insulating sheath 52 is cut by inner edges of the slots 41a, so that the conductor 51 in the insulating sheath 52 is brought into contact with the inner edges of the slots 41a, thereby making an electrical connection between the conductor 51 and the insulation displacement connecting terminal 40.
Examples of defective insulation displacement connection, developing during the above insulation displacement connecting operation, are as follows.
For some reason, if any of the wires, fed to the insulation displacement connecting step, is inserted in a twisted condition into the slots to be insulation-displacement-connected to the terminal, the wire can be press-fitted excessively or inadequately. Also, there is a possibility that the wire fails to be inserted into the slots, and the empty hitting occurs, so that a wire-absent condition develops. Alternatively, there can be encountered abnormal insulation displacement connection in which the wire to be inserted into the adjoining cavity is inserted, together with the proper wire, into one slot, so that the double wire-hitting occurs.
In the conventional insulation displacement connection examination, it is judged that the insulation displacement connection is finished when the insulation displacement connecting blade for press-fitting the wire into the slots, reaches its lower dead point. With this method, however, the above deficiencies can not be detected.
For example, in the case of xe2x80x9cwire absencexe2x80x9d, the insulation displacement connecting blade reaches the lower dead point without undergoing any resistance, and even in the case of the abnormal insulation displacement connection (double wire-hitting), the insulation displacement connecting condition is not different from the proper insulation displacement connecting condition for one wire if the wires are soft, and if the force for pressing the insulation displacement connecting blade is extremely large.
It is therefore an object of this invention to provide a method of examining defective insulation displacement connection developing during the insulation displacement connecting operation, and also to provide an apparatus for performing this method.
In the present invention, in order to solve the above problems, by measuring a height of an upper surface of the insulation displacement connected wire from a reference position, the examination of the insulation displacement connection is effected. With this method, the presence of the wire can be directly detected, and therefore information of the insulation displacement connecting height, the wire presence/absence, the abnormal insulation displacement connection and the wire projecting amount, which represent the insulation displacement connected condition, can be obtained.
xe2x80x9cThe insulation displacement connecting heightxe2x80x9d is the height of the upper surface of the wire sheath from the reference position at the position of the slot. The reference position in the direction of the height may be any arbitrary position in the space, and can be, for example, an upper surface of a connector-positioning pallet (the bottom surface of the connector).
In the case where the connector (not shown) is of such a design that two terminals 41 are juxtaposed and spaced a distance D1 from each other in the direction of the length of the wire 50 so that the wire can be insulation-displacement-connected at two portions thereof as shown in FIG. 5, the measurement position in the horizontal direction is a middle position Al between the two terminals 41 and 41. In the case where only one terminal 41 is attached to the wire 50 in the direction of the length of the wire, the measurement position in the horizontal direction is a position A2 at which this terminal 41 exists.
With respect to xe2x80x9cthe wire presence/absencexe2x80x9d, if the wire is present, it is necessarily detected in the measurement of the wire insulation displacement connecting height. If the wire is absent, it detected when the height of the wire sheath from the reference position, measured in this measurement, represents a value smaller than its normal value by an amount equal to the normal outer diameter of the wire.
xe2x80x9cThe abnormal insulation displacement connectionxe2x80x9d is encountered, for example, if a plurality of wires are insulation-displacement-connected in a bundled manner into one slot, and in this case, the position of the sheath of the uppermost wire is measured, and therefore the measured value of the above insulation displacement connecting height is extraordinarily large, and therefore it is judged that this is the abnormal insulation displacement connection.
Although xe2x80x9cthe wire projecting amountxe2x80x9d is the amount of projecting of the wire from the side surface of the terminal, this amount itself is not measured, and as shown in FIG. 5, a position B, obtained by subtracting an absolute value a of a tolerance from a normal projecting position (that is, a position advanced a normal projecting amount D2 from the side surface of the terminal 41 in the direction of projecting of the wire 50), is defined as an examination position, and at this position B, the presence/absence of the wire 50 is detected according to the same procedure as described above for the examination of xe2x80x9cthe wire presence/absencexe2x80x9d, and the judgment is made based on this. More specifically, if the presence of the wire 50 at the examination position B is confirmed, it is decided that the projecting amount is normal, and if it is judged that the wire 50 is absent, it is decided that the projecting amount is not normal.
If not less than two of the wire insulation displacement connecting height, the wire projecting amount, the wire presence/absence and the abnormal wire insulation displacement connection are measured, the defective insulation displacement connection can be detected multilaterally, and the product of a high quality can be obtained.
In order to effect the above examination, there is used the apparatus provided with the CCD laser displacement gauge movable in the direction of juxtaposition of the wires.
In this apparatus, the CCD laser displacement gauge is scanningly moved in the direction of juxtaposition of the wires so that the measurements in the above Items can be made.
The reasons why the laser displacement gauge is used are that it is not desirable to apply a load to the wire at the insulation displacement connecting position and that not a contact-type (which applies a load) but a non-contact-type measurement instrument need to be used. The reasons why the CCD system is used are that the amount of light for each picture element can be detected and that even if the light amount varies depending on the surface condition of the object to be measured, the position where the light amount is at a peak can be accurately detected. In the insulation displacement connecting position, the insulation displacement connected wire is pressed by the insulation displacement connecting blade, and also receives forces from the inner edges of the slot, so that the surface of the wire is not flat, and therefore the function of the CCD system is needed.
Although various colors and patterns are used for the sheath of the wires of the wire harness, the CCD laser system is not influenced by these elements.
The present disclosure relates to the subject matter contained in Japanese patent application No. Hei. 11-13304 (filed on Jan. 21, 1999) which is expressly incorporated herein by reference in its entirely.